A 0.9-2.6 GHz Cognitive Radio Receiver With Spread Spectrum Frequency Synthesizer for Spectrum Sensing

In this paper, 0.9-2.6 GHz receiver with spread spectrum frequency synthesizer is proposed for spectrum sensing cognitive radio system. With the presence of spread spectrum window generated by local synthesizer, the bandwidth of low-pass filter for spectrum sensing can be fixed, which alleviates the complexity of energy detection block, making it easily embedded into a transceiver chip. The proposed coherent sampling quickens energy detection under negative signal-to-noise ratio. The proposed direct conversion receiver with wideband interference rejection includes a low noise amplifier and mixer, which achieves a NF of 5 dB and gain of 30 dB over the entire bandwidth with 20 mW power consumption. The ultra-wideband voltage controlled oscillator with loss compensation is designed to cover 0.9-2.6 GHz. A prototype chip has been fabricated in 0.18 μm CMOS technology consuming 130 mW in sensing mode with 1.8 V power supply. The total chip area including pads is approximately 2.75 mm 2 . The proposed CR receiver achieves wide operation frequency range from 900 MHz to 2.6 GHz with minimum detection sensitivity of -93.2 dBm and adjustable detection window of 35~70 MHz.